TPI5speedguys

I have a couple slight issues. When i'm cruising around or above 2000 rpm's the cars tac will jump up sporatically about 3-5000 rpm's. It does this really randomly also, some days it won't do it at all and on other days it will. It sometimes will also drive fine for an hour then suddenly do it again. The engine will not drop below my cruising rpm just up. Sounds like there is some slight overfueling. What could be the possible cause? Also, the car surges a bit at idle and idles a bit high around 1400 rpms. I believe it may be the IAC valve is there any other possibilities though?

Thanks

bigreed91

when the rpms jump while driving can you actually hear it revving? if not id say electrical tach issue, if you do, does the speed increase or stay the same (can you feel it jerk like your hitting the gas?) if the the rpms are jumping that high but no speed increase is felt it sounds like your torque converter is slipping or some other tranny related issue. im not very tranny savy but thats what it sounds like to me

TPI5speedguys

No I can't hear it to much, it is really quick revs. But it is jerky though and the speed doesn't increase noticeably because of how quick it is. Also, I have a 5 speed so it can't be the torque converter.

TPI5speedguys

Hey, just a quick thought, I also have a slight throttle lag when I initially step on the gas pedal as well, could this possible all be contributed to the trottle position sensor (TPS)?

Thanks

TPI5speedguys

Another note, it's been getting colder and has not done it at all but the other day it got a little warmer and it did it a bit. Any ideas?

UnderCover89TBI

iTrader: (25)

well can you confirm the engine rpm is actually going up, or is the tachometer just malfunctioning?

rpm's would jump up if more air was introduced into the system, so i'd look into a possible vacuum leak

one92rs

iTrader: (5)

are you sure you dont have a clutch issue?

mikesanto70

Hi, I have a 1991 5.0 LO3 Camaro RS and it is idling high and it will stumble when I take off from a stop, and at 35 mph, i can let of the gas and maintain my speed if the road stays flat. I have new plugs and EGR so those can be eliminated. A friend suggested a vaccuum leak too, where should i be looking and how to check. He said to spray starting fluid on vac lines and base of tbi to see if gasket leaking too. What do u think?

TPI5speedguys

Actually upon further inspection I can tell there is a tach malfunction, but when it malfunctions there is occasionally a slight stutter in the motor, could these possible be related? Just a quick note I have changed plugs, wires, cap, rotor, and coil within the last 6 months, I changed the coil because it was causing my car to severely cut out.

mikesanto70

I cleaned the IAC and while also spraying brake cleaner near the base of the TBI unit it revved up a little which told me I had a TBI Base Gasket leak too. So after cleaning the IAC it still was high, i went into the garage to call pep boys to check on base gasket then got in car to go pick it up and it was idling normal again. The IAC cleaning did the trick, but I still had a slight base gasket leak so I changed it and sure enough, it needed to be done but was not terrible, but needed it, so now it runs like a champ. Thanks for the help!!!!!!
Mike Santo